Lookng at the caps I would also say British SU's. I'm not sure how much better the british ones are than the old flat tops but most people install the Japanese 240 carbs look the same with a couple of variations of 3 or 4 screw type, both work same from what I've heard.
If you've done some work on the motor and need more fuel I think people change the needles in these carbs (SM needles from memory, as to who sells these needles etc I have no idea).
Good Luck,
Sulio